[XviD-devel] New QPel code?

[Christoph Lampert]

Hi,

latest CVS with QPel crashes with max_b=-1 for me, and 
Qpel doesn't seem to work with max_b>=0.


Something else: 

In motion_comp for INTER4V there is

		
		sum = mvs[0].x + mvs[1].x + mvs[2].x + mvs[3].x;

		if(quarterpel)
			sum /= 2;

		dx = (sum ? SIGN(sum) *
			  (roundtab[ABS(sum) % 16] + (ABS(sum) / 16)*2) : 0);


Are you sure quarterpel _or_ halfpel are rounded correctly here? 

no QPel:  mvs[0-3].x are in halfpel resolution, then 
sum/4  would be  eigthpel and should be rounded using 

Table 7-8 
"Modification of eigth sample resolution chrominance vector components"

Why do we use 16th-pel table for everything?  


Whereas for Quarterpel,  (mvs[0].x + mvs[1].x+mvs[2].x+mvs[3].x ) /4
would be sixteenthpel res and the 16-table should be used?

Simply dividing sum/2 and _then_ rounding again is surely wrong, too,
isn't it? 


gruel